The natural ocean soundscape is crucial to the health of marine life, but a first-of-its-kind comprehensive literature review finds that human activities are creating increasingly loud and harmful noise in the ocean. Marine life communicates through sound, and noise pollution acts like an "acoustic fog" in the ocean. Scientists say noise is as harmful as overfishing, pollution, and the climate crisis, yet is often overlooked. The good news is that, compared to other issues, noise can be stopped immediately and has fewer lingering effects. Marine animals can hear at a much greater distance than their vision or smell, making sound integral to every aspect of their lives. From whales to shellfish, marine life relies on sound to catch prey, navigate, defend their territories, attract mates, return to breeding grounds, and warn of attacks. Noise pollution increases the risk of death and, in extreme cases, such as explosions, can cause death directly. Researchers say that carbon dioxide emissions from fossil fuel combustion are making the oceans more acidic, which in turn causes sound to travel farther through the water, making the oceans noisier. However, when maritime traffic plummeted due to the COVID-19 pandemic, marine mammals and sharks began migrating to previously noisy areas, suggesting that marine life can quickly recover from noise pollution. "From plankton to sharks, all organisms can sense the sounds in their environment," said Professor Steve Simpson of the University of Exeter in England. Animals rely on sound to communicate, and noise pollution acts like an "acoustic fog" in the ocean. Scientists analyzed 500 papers, and 90% of the studies showed that noise is harmful to marine mammals. Professor Carlos Duarte of King Abdullah University of Science and Technology said: "Marine animals can only see things tens of meters away and smell things hundreds of meters away, but they can hear sounds from the entire ocean basin." Duarte believes that many important studies evaluating the health of the ocean have ignored noise, but there is strong evidence in the literature that human-induced noise is one of the main disruptors of marine ecosystems. This retrospective study, published in the journal Science, analyzed more than 500 papers evaluating the impact of noise on marine life. Approximately 90% of studies found significant harms to marine mammals such as whales, seals, and dolphins, while 80% reported impacts on fish and invertebrates. The analysis concluded, "Sound is a fundamental element of ecosystems, and its impact is pervasive, affecting animals at various levels." Most notably, military sonar and seismic blasting are linked to deafness, mass strandings, and marine mammal mortality. Many other sound-related habits may also be affected, such as the buzzing of male toadfish to attract females and the calls of cod used to regulate spawning. Whale calls promote group cohesion and reproductive success and can be transmitted across oceans. Humpback whale mating songs are so complex they even have regional dialects. Sperm whales and various dolphins and porpoises use sonar to echolocate their prey, and some shrimp can produce a "pop" sound to stun their prey. Noise levels on major shipping routes have increased 32-fold over the past 50 years. Research continues to propose solutions. However, over the past 50 years, increased ocean shipping has increased low-frequency noise on major shipping routes by 32-fold. Fishing boats use sonar to locate schools of fish, and trawlers create a rumbling noise. The construction and operation of oil rigs and offshore wind farms create noise pollution comparable to the bomb explosions in the North Sea during World War II. "Fish, clams, crabs, and corals all hear and use sound to find healthy habitats, and shipping or construction noise disrupts this ability," Simpson said. "This also means that families of whales that once hunted hundreds of miles away can now only communicate within 10 miles of each other." "We've found that animals are directly stressed by noise, making poor decisions that can lead to mortality," he said, noting that noise from jet skis on Australia's Great Barrier Reef can double the mortality rate of predators. The study also found that solutions are possible. In 2015, shipping giant Fastmast retrofitted five large container ships with new propeller designs that reduced noise and improved fuel efficiency. Duarte said quiet propellers are paramount. Furthermore, half of shipping noise comes from just 15% of ships. Electric motors and slightly slower speeds can also improve things. Between 2007 and 2013, a reduction in Mediterranean ship speed from 15.6 knots to 13.8 knots reduced noise by 50%. Seismic surveys can also be conducted using seabed vibrators, rather than transmitting noise waves through the water column. Source: Environmental Information Center, UK Guardian
